Prevent automatic simplification of a symbolic expression when using the latex command

I have the following expression

f = @(k,n)1.0./n.^(2.0./3.0).*(6.0.^(1.0./3.0).*k.^(1.0./3.0).*4.0-k.*n.^(2.0./3.0).*1.2e1).*(-1.0./3.0)

and when I write

latex(f(k,n))

I get the hideous expression

\frac{12\, k\, n^{\frac{2}{3}} - \frac{8183583624766079\, k^{\frac{1}{3}}}{1125899906842624}}{3\, n^{\frac{2}{3}}}

Obviously matlab is doing some simplifications along the way. Is there any way to get the latex command to output the original expression for f that I typed in, without making any simplifications?

Thanks for any advice

Answer 1

[Walter Roberson]

No, that is not possible in any easy way.

When you invoked f(k,n) to turn the function handle into a sym so you could call latex(), then you requested evaluation of the function. Evaluation of symbolic functions always involves automatic simplification of constant expressions and automatic combination of constant terms, along with various automatic rewriting of term order according to rules that can be difficult to work out.

I have to wonder, though, where that code came from? It looks suspiciously like something that would be generated by matlabFunction() applied to a symbolic expression; if so then possibly you can latex() the symbolic expression directly.

[Leo Simon]

Thanks, Walter. You're right it was generated by matlabFunction, which took a derivative for me. Here's the code snippet. I doubt that I can apply latex directly to this, but I'll post it just in case.

   syms k_r k_n n positive
      assumeAlso(k_n > k_r);
      f                   = @(k_r,n) -sym(2)*( sym(6)^(sym(1)/sym(3))/sym(2)*  (n*abs(k_r)).^(-sym(2)/sym(3)) - sym(1) ).*k_r.^sym(2) ;
      df                  = matlabFunction(simplify(diff(f(k_r,n),k_r)));

[Walter Roberson]

syms k_r k_n n positive
assumeAlso(k_n > k_r);
f = @(k_r,n) -sym(2)*( sym(6)^(sym(1)/sym(3))/sym(2)*  (n*abs(k_r)).^(-sym(2)/sym(3)) - sym(1) ).*k_r.^sym(2) ;
df_form = simplify(diff(f(k_r,n),k_r));
df_latex = latex(df_form);
df = matlabFunction(df_form);

[Leo Simon]

Perfect, thanks!